Abstract-Metamaterial composite bandpass filter with an ultra-broadband rejection bandwidth of up to 240 terahertz

Andrew C. Strikwerda^1,a), Maksim Zalkovskij¹, Dennis Lund Lorenzen¹,

Alexander Krabbe¹, Andrei V. Lavrinenko¹ and Peter Uhd Jepsen¹


1 DTU Fotonik—Department of Photonics Engineering, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark
a) Author to whom correspondence should be addressed. Electronic mail: astr@fotonik.dtu.dk.
Appl. Phys. Lett. 104, 191103 (2014); http://dx.doi.org/10.1063/1.4875795

http://scitation.aip.org/content/aip/journal/apl/104/19/10.1063/1.4875795

We present a metamaterial, consisting of a cross structure and a metal mesh filter, that forms a composite with greater functional bandwidth than any terahertz (THz) metamaterial to date.Metamaterials traditionally have a narrow usable bandwidth that is much smaller than commonTHz sources, such as photoconductive antennas and difference frequency generation. The composite structure shown here expands the usable bandwidth to exceed that of current THz sources. To highlight the applicability of this combination, we demonstrate a series ofbandpass filters with only a single pass band, with a central frequency (f0 ) that is scalable from 0.86–8.51 THz, that highly extinguishes other frequencies up to >240 THz. The performance of these filters is demonstrated in experiment, using both air biased coherent detection and a Fourier transform infrared spectrometer (FTIR), as well as in simulation. We present equations—and discuss their scaling laws—which detail the f0 and full width at half max (Δf) of the pass band, as well as the required geometric dimensions for their fabrication using standard UVphotolithography and easily achievable fabrication linewidths. With these equations, the geometric parameters and Δf for a desired frequency can be quickly calculated. Using thesebandpass filters as a proof of principle, we believe that this metamaterial composite provides the key for ultra-broadband metamaterial design.